The code discovered in the latest El Capitan beta suggests the OS supports a 4096 x 2304 Retina display, a resolution slightly larger than traditional 4K Ultra HD (3840 x 2160) that Apple hasn't used in a product yet. With the 27-inch iMac featuring a 5120 x 2880 display, this new resolution could be used for an upgraded 21.5-inch iMac featuring a Retina display.

At 21.5-inches, a display resolution of 4096 x 2304 would equate to a pixel density of 219 PPI, similar to the 5K 27-inch iMac's 218 PPI. While this 4K-like resolution isn't one we've seen before, Apple usually forgoes industry standard resolutions for pixel density consistency across their Retina products.

The new El Capitan beta also references a selection of new GPUs that haven't been seen in any current-generation iMacs. The GPUs referenced include Intel's new Iris Pro Graphics 6200 found in their new Broadwell CPUs, and new AMD Radeon GPUs including the R9 M395 and R9 M395X.

On a less exciting note, El Capitan contains a few references to a new Apple Bluetooth Remote Control as well, featuring Bluetooth and infrared connectivity, and a multi-touch trackpad.

There are no hints as to when Apple may announce a new 21.5-inch iMac or a new Bluetooth Remote Control, although Apple typically announces new iMacs around October. El Capitan is set for a final release this fall.